Prosthetic joints with contained compressible resilient members

Abstract

In a total knee replacement (TKR), the use of a cushion element provides better wear characteristics than polyethylene (“poly”) alone. Since a metal-on-metal, metal-on-ceramic, or ceramic-on-ceramic articulating surface has better wear characteristics than metal on poly, the invention essentially provides cushioning for metal / ceramic-on-metal / ceramic joint replacements. It also allows the use of elastomers for their cushioning properties rather than their surface wear and tensile strength characteristics. The contained compressible elements could also be used as a cushion below polyethylene components, polyethylene over metal components, unicondylar knee replacements, patellar components, and prosthetic components for other parts of the body, including the hip, elbow, shoulder, wrist, and ankle.

Description

REFERENCE TO RELATED APPLICATION [0001] This application claims priority from U.S. Provisional Patent Application Ser. Nos. 60 / 379,462, filed May 10, 2002; 60 / 445,489, filed Feb. 6, 2003; and 60 / 445,958, filed Feb. 7, 2003. This application is also a continuation-in-part of U.S. patent application Ser. No. 10 / 407,554, filed Apr. 4, 2003, which is a continuation-in-part of U.S. patent application Ser. No. 10 / 303,385, filed Nov. 25, 2002; which is a continuation-in-part of U.S. patent application Ser. No. 10 / 191,639, filed Jul. 9, 2002 and Ser. No. 09 / 415,382, filed Oct. 8, 1999, now U.S. Pat. No. 6,419,704. The entire content of each application and patent is incorporated herein by reference.FIELD OF THE INVENTION [0002] This invention relates generally to prosthetic implants and, more particularly, to devices of this type including contained, compressible, resilient members. BACKGROUND OF THE INVENTION [0003] In prior art total knee replacements (TKRs), polyethylene trays are placed...

AI Technical Summary

Benefits of technology

[0008] The cushion elements in the preferred embodiments include synthetic rubbers, hydrogels, elastomers, and other polymeric materials such as viscoelastic polymers and foam polyurethanes. The invention effectively combines the advantages of such materials (cushioning, shape memory, and expansion after insertion in the case of hydrogels), while providing increased protection, particularly the elimination of shear stresses.

[0009] In a total knee replacement (TKR), the use of a cushion element provides better wear characteristics than polyethylene (“poly”) alone. Since a metal-on-metal, metal-on-ceramic, or ceramic-on-ceramic articulating surface has better wear characteristics than metal on poly, the invention essentially provides cushioning for metal / ceramic-on-metal / ceramic joint replacements. It also allows the use of elastomers for their cushioning properties rather than their surface wear and tensile strength characteristics.

Problems solved by technology

The loads across the TKR and movement between the femoral component and poly tray cause surface wear of the poly.

The problems associated with poly wear are well known to Orthopaedic surgeons: fracture of the poly tray, thinning of the tray, migration of poly particles throughout the body, and loosening of the prosthetic joint from the body's reaction to the poly particles.

Metal on metal articulations are reported to have 400× less wear than metal on poly surfaces, but their use has so far been limited.

Metal-on-metal designs do not provide dampening.

Metal-on-poly surfaces provide more dampening than metal on metal surfaces, but they do not the cushioning of cartilage.

The choice of materials for prosthetic implants is also limited by surface wear characteristics of the materials.

Metals have better surface wear characteristics than polyethylene, but metals do not provide cushioning.

The choice of materials is also limited by the tensile strength of the materials.

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